The 747-100 was the original variant launched in 1966. The first 747-100s were built with six upper deck windows (three per side) to accommodate upstairs lounge areas. Later, as airlines began to use the upper deck for premium passenger seating instead of lounge space, Boeing offered a ten-window upper deck as an option.
To install this aircraft, download the .zip archive to your local hard drive, and extract them into your Aircraft folder. For windows users, this will be located in C:\Program Files\FlightGear\data\Aircraft.